From 265ff6329cb634a81242bf80e5bc297d4020270e Mon Sep 17 00:00:00 2001
From: Vladimir Agafonkin <agafonkin@gmail.com>
Date: Tue, 26 May 2026 20:32:10 +0300
Subject: [PATCH 1/5] add nextField and skipField helpers

---
 README.md                          | 76 +++++++++++++++++-------------
 compile.js                         |  7 ++-
 index.js                           | 30 ++++++++----
 test/fixtures/defaults.js          |  6 +--
 test/fixtures/defaults_implicit.js | 12 ++---
 test/fixtures/defaults_proto3.js   |  6 +--
 test/fixtures/embedded_type.js     | 18 +++----
 test/fixtures/map.js               | 18 +++----
 test/fixtures/map_collision.js     | 24 +++++-----
 test/fixtures/oneof.js             |  6 +--
 test/fixtures/packed.js            | 18 +++----
 test/fixtures/packed_proto3.js     | 24 +++++-----
 test/fixtures/type_string.js       | 12 ++---
 test/fixtures/varint.js            |  6 +--
 test/fixtures/vector_tile.js       | 24 +++++-----
 test/pbf.test.js                   | 38 +++++++++++++++
 16 files changed, 193 insertions(+), 132 deletions(-)

diff --git a/README.md b/README.md
index a3e3200..c238be0 100644
--- a/README.md
+++ b/README.md
@@ -61,16 +61,29 @@ const {readExample, writeExample} = compile(proto);
 #### Custom Reading
 
 ```js
-const data = new PbfReader(buffer).readFields(readData, {});
-
-function readData(tag, data, pbf) {
-    if (tag === 1) data.name = pbf.readString();
-    else if (tag === 2) data.version = pbf.readVarint();
-    else if (tag === 3) data.layer = pbf.readMessage(readLayer, {});
+const pbf = new PbfReader(buffer);
+const data = readData(pbf);
+
+function readData(pbf, end = pbf.length) {
+    const data = {};
+    let field;
+    while ((field = pbf.nextField(end))) {
+        if (field === 1) data.name = pbf.readString();
+        else if (field === 2) data.version = pbf.readVarint();
+        else if (field === 3) data.layer = readLayer(pbf, pbf.readVarint() + pbf.pos);
+        else pbf.skipField();
+    }
+    return data;
 }
-function readLayer(tag, layer, pbf) {
-    if (tag === 1) layer.name = pbf.readString();
-    else if (tag === 3) layer.size = pbf.readVarint();
+function readLayer(pbf, end) {
+    const layer = {};
+    let field;
+    while ((field = pbf.nextField(end))) {
+        if (field === 1) layer.name = pbf.readString();
+        else if (field === 3) layer.size = pbf.readVarint();
+        else pbf.skipField();
+    }
+    return layer;
 }
 ```
 
@@ -137,29 +150,23 @@ pbf.pos; // current offset for reading or writing
 
 #### Reading
 
-Read a sequence of fields:
+Loop over a message's fields with `nextField`, dispatch on the field number, and call `skipField()` for anything you don't recognize:
 
 ```js
-pbf.readFields((tag) => {
-    if (tag === 1) pbf.readVarint();
-    else if (tag === 2) pbf.readString();
-    else ...
-});
+let field;
+while ((field = pbf.nextField(end))) {
+    if (field === 1) obj.id = pbf.readVarint();
+    else if (field === 2) obj.name = pbf.readString();
+    else pbf.skipField();
+}
 ```
 
-It optionally accepts an object that will be passed to the reading function for easier construction of decoded data,
-and also passes the `PbfReader` object as a third argument:
+To read an embedded message, pass `pbf.readVarint() + pbf.pos` as `end` to a nested reader:
 
 ```js
-const result = pbf.readFields(readField, {})
-
-function readField(tag, result, pbf) {
-    if (tag === 1) result.id = pbf.readVarint();
-}
+const msg = readSubMessage(pbf, pbf.readVarint() + pbf.pos);
 ```
 
-To read an embedded message, use `pbf.readMessage(fn[, obj])` (in the same way as `read`).
-
 Read values:
 
 ```js
@@ -168,19 +175,22 @@ const str = pbf.readString();
 const numbers = pbf.readPackedVarint();
 ```
 
-For lazy or partial decoding, simply save the position instead of reading a value,
-then later set it back to the saved value and read:
+For lazy or partial decoding, save the position and come back to it later:
 
 ```js
-const fooPos = -1;
-pbf.readFields((tag) => {
-    if (tag === 1) fooPos = pbf.pos;
-});
+let fooPos = -1;
+let field;
+while ((field = pbf.nextField())) {
+    if (field === 1) fooPos = pbf.pos;
+    pbf.skipField();
+}
 ...
 pbf.pos = fooPos;
-pbf.readMessage(readFoo);
+const foo = readFoo(pbf, pbf.readVarint() + pbf.pos);
 ```
 
+A callback-based `readFields(fn, obj, end)` is also available for backward compatibility, but new code should prefer the `nextField` loop — it's significantly faster.
+
 Scalar reading methods:
 
 * `readVarint(isSigned)` (pass `true` if you expect negative varints)
@@ -194,7 +204,9 @@ Scalar reading methods:
 * `readDouble()`
 * `readString()`
 * `readBytes()`
-* `skip(value)`
+* `nextField(end)` — returns the next field number, or `0` at end-of-message
+* `skipField()` — skips the current field
+* `skip(value)` — skips a field given its raw tag varint
 
 Packed reading methods:
 
diff --git a/compile.js b/compile.js
index c0559d0..e238c51 100644
--- a/compile.js
+++ b/compile.js
@@ -29,17 +29,16 @@ function writeMessage(ctx, options) {
 
     if (!options.noRead) {
         const readName = `read${ctx._name}`;
-        const hasPackable = fields.some(f => f.repeated && willSupportPacked(ctx, f));
 
         code += `${writeFunctionExport(options, readName)}function ${readName}(pbf, end = pbf.length) {\n`;
         code += `    const obj = ${compileDest(ctx)};\n`;
-        code += '    while (pbf.pos < end) {\n';
-        code += `        const tag = pbf.readVarint(), field = tag >>> 3${hasPackable ? '; pbf.type = tag & 7' : ''};\n`;
+        code += '    let field;\n';
+        code += '    while ((field = pbf.nextField(end))) {\n';
 
         for (let i = 0; i < fields.length; i++) {
             code += `        ${i ? 'else ' : ''}if (field === ${fields[i].tag}) ${compileFieldRead(ctx, fields[i])}\n`;
         }
-        code += `        ${fields.length ? 'else ' : ''}pbf.skip(tag);\n`;
+        code += `        ${fields.length ? 'else ' : ''}pbf.skipField();\n`;
         code += '    }\n    return obj;\n}\n';
     }
 
diff --git a/index.js b/index.js
index 2a623f7..723f73d 100644
--- a/index.js
+++ b/index.js
@@ -31,15 +31,11 @@ export class PbfReader {
      * @param {number} [end]
      */
     readFields(readField, result, end = this.length) {
-        while (this.pos < end) {
-            const val = this.readVarint(),
-                tag = val >> 3,
-                startPos = this.pos;
-
-            this.type = val & 0x7;
-            readField(tag, result, this);
-
-            if (this.pos === startPos) this.skip(val);
+        let field;
+        while ((field = this.nextField(end))) {
+            const startPos = this.pos;
+            readField(field, result, this);
+            if (this.pos === startPos) this.skipField();
         }
         return result;
     }
@@ -200,6 +196,22 @@ export class PbfReader {
         return this.type === PBF_BYTES ? this.readVarint() + this.pos : this.pos + 1;
     }
 
+    /**
+     * Advance to the next field. Returns the field number, or 0 at end-of-message.
+     * @param {number} [end]
+     */
+    nextField(end = this.length) {
+        if (this.pos >= end) return 0;
+        const tag = this.readVarint();
+        this.type = tag & 0x7;
+        return tag >>> 3;
+    }
+
+    /** Skip the field most recently returned by `nextField`. */
+    skipField() {
+        this.skip(this.type);
+    }
+
     /** @param {number} val */
     skip(val) {
         const type = val & 0x7;
diff --git a/test/fixtures/defaults.js b/test/fixtures/defaults.js
index 67946d6..88ff5a6 100644
--- a/test/fixtures/defaults.js
+++ b/test/fixtures/defaults.js
@@ -6,14 +6,14 @@ export const MessageType = {
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {type: 1, name: "test", flag: true, weight: 1.5, id: 1};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.type = pbf.readVarint();
         else if (field === 2) obj.name = pbf.readString();
         else if (field === 3) obj.flag = pbf.readBoolean();
         else if (field === 4) obj.weight = pbf.readFloat();
         else if (field === 5) obj.id = pbf.readVarint(true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/defaults_implicit.js b/test/fixtures/defaults_implicit.js
index ba6ec02..ba2992d 100644
--- a/test/fixtures/defaults_implicit.js
+++ b/test/fixtures/defaults_implicit.js
@@ -6,9 +6,9 @@ export const MessageType = {
 
 export function readCustomType(pbf, end = pbf.length) {
     const obj = {};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
-        pbf.skip(tag);
+    let field;
+    while ((field = pbf.nextField(end))) {
+        pbf.skipField();
     }
     return obj;
 }
@@ -17,8 +17,8 @@ export function writeCustomType(obj, pbf) {
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {type: 0, name: "", flag: false, weight: 0, id: 0, tags: [], numbers: [], bytes: undefined, custom: undefined, types: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.type = pbf.readVarint();
         else if (field === 2) obj.name = pbf.readString();
         else if (field === 3) obj.flag = pbf.readBoolean();
@@ -29,7 +29,7 @@ export function readEnvelope(pbf, end = pbf.length) {
         else if (field === 8) obj.bytes = pbf.readBytes();
         else if (field === 9) obj.custom = readCustomType(pbf, pbf.readVarint() + pbf.pos);
         else if (field === 10) pbf.readPackedVarint(obj.types);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/defaults_proto3.js b/test/fixtures/defaults_proto3.js
index 0827af1..1f7faab 100644
--- a/test/fixtures/defaults_proto3.js
+++ b/test/fixtures/defaults_proto3.js
@@ -6,14 +6,14 @@ export const MessageType = {
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {type: 0, name: "", flag: false, weight: 0, id: 0};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.type = pbf.readVarint();
         else if (field === 2) obj.name = pbf.readString();
         else if (field === 3) obj.flag = pbf.readBoolean();
         else if (field === 4) obj.weight = pbf.readFloat();
         else if (field === 5) obj.id = pbf.readVarint(true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/embedded_type.js b/test/fixtures/embedded_type.js
index 5ede605..f95c987 100644
--- a/test/fixtures/embedded_type.js
+++ b/test/fixtures/embedded_type.js
@@ -1,12 +1,12 @@
 
 export function readEmbeddedType(pbf, end = pbf.length) {
     const obj = {value: "test", sub_field: undefined, sub_sub_field: undefined};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.value = pbf.readString();
         else if (field === 4) obj.sub_field = readEmbeddedTypeContainer(pbf, pbf.readVarint() + pbf.pos);
         else if (field === 5) obj.sub_sub_field = readEmbeddedTypeContainerInner(pbf, pbf.readVarint() + pbf.pos);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -18,10 +18,10 @@ export function writeEmbeddedType(obj, pbf) {
 
 export function readEmbeddedTypeContainer(pbf, end = pbf.length) {
     const obj = {values: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.values.push(readEmbeddedTypeContainerInner(pbf, pbf.readVarint() + pbf.pos));
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -31,10 +31,10 @@ export function writeEmbeddedTypeContainer(obj, pbf) {
 
 export function readEmbeddedTypeContainerInner(pbf, end = pbf.length) {
     const obj = {value: ""};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.value = pbf.readString();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/map.js b/test/fixtures/map.js
index 04b254b..e452ea2 100644
--- a/test/fixtures/map.js
+++ b/test/fixtures/map.js
@@ -1,11 +1,11 @@
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {kv: {}, kn: {}};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) { const {key, value} = readEnvelopeKvEntry(pbf, pbf.readVarint() + pbf.pos); obj.kv[key] = value; }
         else if (field === 2) { const {key, value} = readEnvelopeKnEntry(pbf, pbf.readVarint() + pbf.pos); obj.kn[key] = value; }
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -16,11 +16,11 @@ export function writeEnvelope(obj, pbf) {
 
 export function readEnvelopeKvEntry(pbf, end = pbf.length) {
     const obj = {key: "", value: ""};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readString();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -31,11 +31,11 @@ export function writeEnvelopeKvEntry(obj, pbf) {
 
 export function readEnvelopeKnEntry(pbf, end = pbf.length) {
     const obj = {key: "", value: 0};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readVarint(true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/map_collision.js b/test/fixtures/map_collision.js
index 2347a83..d3b569f 100644
--- a/test/fixtures/map_collision.js
+++ b/test/fixtures/map_collision.js
@@ -1,13 +1,13 @@
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {kv: {}, kn: {}, sibling: undefined, flag: 0};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) { const {key, value} = readEnvelopeKvEntry$(pbf, pbf.readVarint() + pbf.pos); obj.kv[key] = value; }
         else if (field === 2) { const {key, value} = readEnvelopeKnEntry$(pbf, pbf.readVarint() + pbf.pos); obj.kn[key] = value; }
         else if (field === 3) obj.sibling = readEnvelopeKvEntry(pbf, pbf.readVarint() + pbf.pos);
         else if (field === 4) obj.flag = pbf.readVarint();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -25,10 +25,10 @@ export const EnvelopeKnEntry = {
 
 export function readEnvelopeKvEntry(pbf, end = pbf.length) {
     const obj = {marker: 0};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.marker = pbf.readVarint(true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -38,11 +38,11 @@ export function writeEnvelopeKvEntry(obj, pbf) {
 
 export function readEnvelopeKvEntry$(pbf, end = pbf.length) {
     const obj = {key: "", value: ""};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readString();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -53,11 +53,11 @@ export function writeEnvelopeKvEntry$(obj, pbf) {
 
 export function readEnvelopeKnEntry$(pbf, end = pbf.length) {
     const obj = {key: "", value: 0};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readVarint(true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/oneof.js b/test/fixtures/oneof.js
index ec8502b..9a6c290 100644
--- a/test/fixtures/oneof.js
+++ b/test/fixtures/oneof.js
@@ -1,13 +1,13 @@
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {id: 0, int: 0, value: undefined, float: 0, string: ""};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.id = pbf.readVarint(true);
         else if (field === 2) { obj.int = pbf.readVarint(true); obj.value = "int"; }
         else if (field === 3) { obj.float = pbf.readFloat(); obj.value = "float"; }
         else if (field === 4) { obj.string = pbf.readString(); obj.value = "string"; }
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/packed.js b/test/fixtures/packed.js
index d8ce77e..6c08a20 100644
--- a/test/fixtures/packed.js
+++ b/test/fixtures/packed.js
@@ -1,11 +1,11 @@
 
 export function readNotPacked(pbf, end = pbf.length) {
     const obj = {value: [], types: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types, true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -16,11 +16,11 @@ export function writeNotPacked(obj, pbf) {
 
 export function readFalsePacked(pbf, end = pbf.length) {
     const obj = {value: [], types: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types, true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -31,11 +31,11 @@ export function writeFalsePacked(obj, pbf) {
 
 export function readPacked(pbf, end = pbf.length) {
     const obj = {value: [], types: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types, true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/packed_proto3.js b/test/fixtures/packed_proto3.js
index e14a56e..120f12a 100644
--- a/test/fixtures/packed_proto3.js
+++ b/test/fixtures/packed_proto3.js
@@ -6,11 +6,11 @@ export const MessageType = {
 
 export function readNotPacked(pbf, end = pbf.length) {
     const obj = {value: [], types: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -21,11 +21,11 @@ export function writeNotPacked(obj, pbf) {
 
 export function readFalsePacked(pbf, end = pbf.length) {
     const obj = {value: [], types: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -36,10 +36,10 @@ export function writeFalsePacked(obj, pbf) {
 
 export function readPacked(pbf, end = pbf.length) {
     const obj = {value: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 16) pbf.readPackedVarint(obj.value, true);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -49,10 +49,10 @@ export function writePacked(obj, pbf) {
 
 export function readPackedFixed(pbf, end = pbf.length) {
     const obj = {value: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedSFixed64(obj.value);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/type_string.js b/test/fixtures/type_string.js
index d8a4228..36f81ac 100644
--- a/test/fixtures/type_string.js
+++ b/test/fixtures/type_string.js
@@ -1,15 +1,15 @@
 
 export function readTypeString(pbf, end = pbf.length) {
     const obj = {int: "0", long: "0", boolVal: false, float: "0", default_implicit: "0", default_explicit: "42"};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.int = pbf.readVarint(true).toString();
         else if (field === 2) obj.long = pbf.readVarint(true).toString();
         else if (field === 3) obj.boolVal = pbf.readBoolean();
         else if (field === 4) obj.float = pbf.readFloat().toString();
         else if (field === 5) obj.default_implicit = pbf.readVarint(true).toString();
         else if (field === 6) obj.default_explicit = pbf.readVarint(true).toString();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -24,13 +24,13 @@ export function writeTypeString(obj, pbf) {
 
 export function readTypeNotString(pbf, end = pbf.length) {
     const obj = {int: 0, long: 0, boolVal: false, float: 0};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.int = pbf.readVarint(true);
         else if (field === 2) obj.long = pbf.readVarint(true);
         else if (field === 3) obj.boolVal = pbf.readBoolean();
         else if (field === 4) obj.float = pbf.readFloat();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/varint.js b/test/fixtures/varint.js
index 5f23f34..ebc31c1 100644
--- a/test/fixtures/varint.js
+++ b/test/fixtures/varint.js
@@ -1,13 +1,13 @@
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {int: 0, uint: 0, long: 0, ulong: 0};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.int = pbf.readVarint(true);
         else if (field === 2) obj.uint = pbf.readVarint();
         else if (field === 3) obj.long = pbf.readVarint(true);
         else if (field === 4) obj.ulong = pbf.readVarint();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/vector_tile.js b/test/fixtures/vector_tile.js
index 4bb2377..64e8909 100644
--- a/test/fixtures/vector_tile.js
+++ b/test/fixtures/vector_tile.js
@@ -1,10 +1,10 @@
 
 export function readTile(pbf, end = pbf.length) {
     const obj = {layers: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 3) obj.layers.push(readTileLayer(pbf, pbf.readVarint() + pbf.pos));
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -21,8 +21,8 @@ export const TileGeomType = {
 
 export function readTileValue(pbf, end = pbf.length) {
     const obj = {string_value: "", float_value: 0, double_value: 0, int_value: 0, uint_value: 0, sint_value: 0, bool_value: false};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.string_value = pbf.readString();
         else if (field === 2) obj.float_value = pbf.readFloat();
         else if (field === 3) obj.double_value = pbf.readDouble();
@@ -30,7 +30,7 @@ export function readTileValue(pbf, end = pbf.length) {
         else if (field === 5) obj.uint_value = pbf.readVarint();
         else if (field === 6) obj.sint_value = pbf.readSVarint();
         else if (field === 7) obj.bool_value = pbf.readBoolean();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -46,13 +46,13 @@ export function writeTileValue(obj, pbf) {
 
 export function readTileFeature(pbf, end = pbf.length) {
     const obj = {id: 0, tags: [], type: 0, geometry: []};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3; pbf.type = tag & 7;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 1) obj.id = pbf.readVarint();
         else if (field === 2) pbf.readPackedVarint(obj.tags);
         else if (field === 3) obj.type = pbf.readVarint();
         else if (field === 4) pbf.readPackedVarint(obj.geometry);
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
@@ -65,15 +65,15 @@ export function writeTileFeature(obj, pbf) {
 
 export function readTileLayer(pbf, end = pbf.length) {
     const obj = {version: 1, name: "", features: [], keys: [], values: [], extent: 4096};
-    while (pbf.pos < end) {
-        const tag = pbf.readVarint(), field = tag >>> 3;
+    let field;
+    while ((field = pbf.nextField(end))) {
         if (field === 15) obj.version = pbf.readVarint();
         else if (field === 1) obj.name = pbf.readString();
         else if (field === 2) obj.features.push(readTileFeature(pbf, pbf.readVarint() + pbf.pos));
         else if (field === 3) obj.keys.push(pbf.readString());
         else if (field === 4) obj.values.push(readTileValue(pbf, pbf.readVarint() + pbf.pos));
         else if (field === 5) obj.extent = pbf.readVarint();
-        else pbf.skip(tag);
+        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/pbf.test.js b/test/pbf.test.js
index ce4a020..77e7950 100644
--- a/test/pbf.test.js
+++ b/test/pbf.test.js
@@ -444,3 +444,41 @@ test('write a raw message > 0x10000000', () => {
     // Then the message itself. Verify that the first few bytes match the marker.
     assert.deepEqual(bytes.subarray(encodedSize.length, encodedSize.length + markerSize), encodedMarker);
 });
+
+test('nextField & skipField', () => {
+    // Encode three fields: varint #1 = 42, string #2 = "hi", varint #3 = 7.
+    const w = new PbfWriter();
+    w.writeVarintField(1, 42);
+    w.writeStringField(2, 'hi');
+    w.writeVarintField(3, 7);
+    const buf = w.finish();
+
+    // Reader that only knows field 1 and field 3 — field 2 must be skipped via skipField.
+    const pbf = new PbfReader(buf);
+    const seen = {};
+    let field;
+    while ((field = pbf.nextField())) {
+        if (field === 1) seen.a = pbf.readVarint();
+        else if (field === 3) seen.b = pbf.readVarint();
+        else pbf.skipField();
+    }
+    assert.deepEqual(seen, {a: 42, b: 7});
+    assert.equal(pbf.pos, buf.length);
+
+    // nextField returns 0 at end-of-message.
+    assert.equal(pbf.nextField(), 0);
+});
+
+test('nextField sets pbf.type for packed reads', () => {
+    // A packed varint field encodes as wire-type 2 (BYTES). readPackedVarint relies on
+    // pbf.type to distinguish packed vs unpacked encodings; nextField must set it.
+    const w = new PbfWriter();
+    w.writePackedVarint(1, [1, 2, 3]);
+    const buf = w.finish();
+
+    const pbf = new PbfReader(buf);
+    const field = pbf.nextField();
+    assert.equal(field, 1);
+    assert.equal(pbf.type, 2); // PBF_BYTES
+    assert.deepEqual(pbf.readPackedVarint(), [1, 2, 3]);
+});

From 45cda1998928c3e2e74de5fbbd62518947469a35 Mon Sep 17 00:00:00 2001
From: Vladimir Agafonkin <agafonkin@gmail.com>
Date: Tue, 26 May 2026 20:49:28 +0300
Subject: [PATCH 2/5] more compact codegen for empty messages

---
 compile.js                         | 32 ++++++++++++++++++++----------
 test/fixtures/defaults_implicit.js | 11 +++-------
 2 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/compile.js b/compile.js
index e238c51..57bf59d 100644
--- a/compile.js
+++ b/compile.js
@@ -31,22 +31,32 @@ function writeMessage(ctx, options) {
         const readName = `read${ctx._name}`;
 
         code += `${writeFunctionExport(options, readName)}function ${readName}(pbf, end = pbf.length) {\n`;
-        code += `    const obj = ${compileDest(ctx)};\n`;
-        code += '    let field;\n';
-        code += '    while ((field = pbf.nextField(end))) {\n';
-
-        for (let i = 0; i < fields.length; i++) {
-            code += `        ${i ? 'else ' : ''}if (field === ${fields[i].tag}) ${compileFieldRead(ctx, fields[i])}\n`;
+        if (fields.length === 0) {
+            code += '    pbf.pos = end;\n    return {};\n';
+        } else {
+            code += `    const obj = ${compileDest(ctx)};\n`;
+            code += '    let field;\n';
+            code += '    while ((field = pbf.nextField(end))) {\n';
+
+            for (let i = 0; i < fields.length; i++) {
+                code += `        ${i ? 'else ' : ''}if (field === ${fields[i].tag}) ${compileFieldRead(ctx, fields[i])}\n`;
+            }
+            code += '        else pbf.skipField();\n';
+            code += '    }\n    return obj;\n';
         }
-        code += `        ${fields.length ? 'else ' : ''}pbf.skipField();\n`;
-        code += '    }\n    return obj;\n}\n';
+        code += '}\n';
     }
 
     if (!options.noWrite) {
         const writeName = `write${ctx._name}`;
-        code += `${writeFunctionExport(options, writeName)}function ${writeName}(obj, pbf) {\n`;
-        for (const field of fields) code += compileFieldWriteLine(ctx, field);
-        code += '}\n';
+        code += `${writeFunctionExport(options, writeName)}function ${writeName}(obj, pbf) {`;
+        if (fields.length === 0) {
+            code += '}\n';
+        } else {
+            code += '\n';
+            for (const field of fields) code += compileFieldWriteLine(ctx, field);
+            code += '}\n';
+        }
     }
     return code;
 }
diff --git a/test/fixtures/defaults_implicit.js b/test/fixtures/defaults_implicit.js
index ba2992d..7a5c764 100644
--- a/test/fixtures/defaults_implicit.js
+++ b/test/fixtures/defaults_implicit.js
@@ -5,15 +5,10 @@ export const MessageType = {
 };
 
 export function readCustomType(pbf, end = pbf.length) {
-    const obj = {};
-    let field;
-    while ((field = pbf.nextField(end))) {
-        pbf.skipField();
-    }
-    return obj;
-}
-export function writeCustomType(obj, pbf) {
+    pbf.pos = end;
+    return {};
 }
+export function writeCustomType(obj, pbf) {}
 
 export function readEnvelope(pbf, end = pbf.length) {
     const obj = {type: 0, name: "", flag: false, weight: 0, id: 0, tags: [], numbers: [], bytes: undefined, custom: undefined, types: []};

From acb6bd6c79b2b0aa431fd5548ddd2eef6b2e682a Mon Sep 17 00:00:00 2001
From: Vladimir Agafonkin <agafonkin@gmail.com>
Date: Tue, 26 May 2026 21:42:18 +0300
Subject: [PATCH 3/5] drop redundant end default

---
 README.md                          | 2 +-
 compile.js                         | 2 +-
 test/fixtures/defaults.js          | 2 +-
 test/fixtures/defaults_implicit.js | 4 ++--
 test/fixtures/defaults_proto3.js   | 2 +-
 test/fixtures/embedded_type.js     | 6 +++---
 test/fixtures/map.js               | 6 +++---
 test/fixtures/map_collision.js     | 8 ++++----
 test/fixtures/oneof.js             | 2 +-
 test/fixtures/packed.js            | 6 +++---
 test/fixtures/packed_proto3.js     | 8 ++++----
 test/fixtures/type_string.js       | 4 ++--
 test/fixtures/varint.js            | 2 +-
 test/fixtures/vector_tile.js       | 8 ++++----
 14 files changed, 31 insertions(+), 31 deletions(-)

diff --git a/README.md b/README.md
index c238be0..9e349ac 100644
--- a/README.md
+++ b/README.md
@@ -64,7 +64,7 @@ const {readExample, writeExample} = compile(proto);
 const pbf = new PbfReader(buffer);
 const data = readData(pbf);
 
-function readData(pbf, end = pbf.length) {
+function readData(pbf, end) {
     const data = {};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/compile.js b/compile.js
index 57bf59d..cdbc4fd 100644
--- a/compile.js
+++ b/compile.js
@@ -30,7 +30,7 @@ function writeMessage(ctx, options) {
     if (!options.noRead) {
         const readName = `read${ctx._name}`;
 
-        code += `${writeFunctionExport(options, readName)}function ${readName}(pbf, end = pbf.length) {\n`;
+        code += `${writeFunctionExport(options, readName)}function ${readName}(pbf, end) {\n`;
         if (fields.length === 0) {
             code += '    pbf.pos = end;\n    return {};\n';
         } else {
diff --git a/test/fixtures/defaults.js b/test/fixtures/defaults.js
index 88ff5a6..61aa3f9 100644
--- a/test/fixtures/defaults.js
+++ b/test/fixtures/defaults.js
@@ -4,7 +4,7 @@ export const MessageType = {
     "GREETING": 1
 };
 
-export function readEnvelope(pbf, end = pbf.length) {
+export function readEnvelope(pbf, end) {
     const obj = {type: 1, name: "test", flag: true, weight: 1.5, id: 1};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/defaults_implicit.js b/test/fixtures/defaults_implicit.js
index 7a5c764..90e325f 100644
--- a/test/fixtures/defaults_implicit.js
+++ b/test/fixtures/defaults_implicit.js
@@ -4,13 +4,13 @@ export const MessageType = {
     "GREETING": 1
 };
 
-export function readCustomType(pbf, end = pbf.length) {
+export function readCustomType(pbf, end) {
     pbf.pos = end;
     return {};
 }
 export function writeCustomType(obj, pbf) {}
 
-export function readEnvelope(pbf, end = pbf.length) {
+export function readEnvelope(pbf, end) {
     const obj = {type: 0, name: "", flag: false, weight: 0, id: 0, tags: [], numbers: [], bytes: undefined, custom: undefined, types: []};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/defaults_proto3.js b/test/fixtures/defaults_proto3.js
index 1f7faab..9e405f4 100644
--- a/test/fixtures/defaults_proto3.js
+++ b/test/fixtures/defaults_proto3.js
@@ -4,7 +4,7 @@ export const MessageType = {
     "GREETING": 1
 };
 
-export function readEnvelope(pbf, end = pbf.length) {
+export function readEnvelope(pbf, end) {
     const obj = {type: 0, name: "", flag: false, weight: 0, id: 0};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/embedded_type.js b/test/fixtures/embedded_type.js
index f95c987..bbff113 100644
--- a/test/fixtures/embedded_type.js
+++ b/test/fixtures/embedded_type.js
@@ -1,5 +1,5 @@
 
-export function readEmbeddedType(pbf, end = pbf.length) {
+export function readEmbeddedType(pbf, end) {
     const obj = {value: "test", sub_field: undefined, sub_sub_field: undefined};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -16,7 +16,7 @@ export function writeEmbeddedType(obj, pbf) {
     if (obj.sub_sub_field) pbf.writeMessage(5, writeEmbeddedTypeContainerInner, obj.sub_sub_field);
 }
 
-export function readEmbeddedTypeContainer(pbf, end = pbf.length) {
+export function readEmbeddedTypeContainer(pbf, end) {
     const obj = {values: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -29,7 +29,7 @@ export function writeEmbeddedTypeContainer(obj, pbf) {
     if (obj.values) for (const item of obj.values) pbf.writeMessage(1, writeEmbeddedTypeContainerInner, item);
 }
 
-export function readEmbeddedTypeContainerInner(pbf, end = pbf.length) {
+export function readEmbeddedTypeContainerInner(pbf, end) {
     const obj = {value: ""};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/map.js b/test/fixtures/map.js
index e452ea2..9db7fe9 100644
--- a/test/fixtures/map.js
+++ b/test/fixtures/map.js
@@ -1,5 +1,5 @@
 
-export function readEnvelope(pbf, end = pbf.length) {
+export function readEnvelope(pbf, end) {
     const obj = {kv: {}, kn: {}};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -14,7 +14,7 @@ export function writeEnvelope(obj, pbf) {
     if (obj.kn) for (const key of Object.keys(obj.kn)) pbf.writeMessage(2, writeEnvelopeKnEntry, {key, value: obj.kn[key]});
 }
 
-export function readEnvelopeKvEntry(pbf, end = pbf.length) {
+export function readEnvelopeKvEntry(pbf, end) {
     const obj = {key: "", value: ""};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -29,7 +29,7 @@ export function writeEnvelopeKvEntry(obj, pbf) {
     if (obj.value) pbf.writeStringField(2, obj.value);
 }
 
-export function readEnvelopeKnEntry(pbf, end = pbf.length) {
+export function readEnvelopeKnEntry(pbf, end) {
     const obj = {key: "", value: 0};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/map_collision.js b/test/fixtures/map_collision.js
index d3b569f..957638f 100644
--- a/test/fixtures/map_collision.js
+++ b/test/fixtures/map_collision.js
@@ -1,5 +1,5 @@
 
-export function readEnvelope(pbf, end = pbf.length) {
+export function readEnvelope(pbf, end) {
     const obj = {kv: {}, kn: {}, sibling: undefined, flag: 0};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -23,7 +23,7 @@ export const EnvelopeKnEntry = {
     "ONE": 1
 };
 
-export function readEnvelopeKvEntry(pbf, end = pbf.length) {
+export function readEnvelopeKvEntry(pbf, end) {
     const obj = {marker: 0};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -36,7 +36,7 @@ export function writeEnvelopeKvEntry(obj, pbf) {
     if (obj.marker) pbf.writeVarintField(1, obj.marker);
 }
 
-export function readEnvelopeKvEntry$(pbf, end = pbf.length) {
+export function readEnvelopeKvEntry$(pbf, end) {
     const obj = {key: "", value: ""};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -51,7 +51,7 @@ export function writeEnvelopeKvEntry$(obj, pbf) {
     if (obj.value) pbf.writeStringField(2, obj.value);
 }
 
-export function readEnvelopeKnEntry$(pbf, end = pbf.length) {
+export function readEnvelopeKnEntry$(pbf, end) {
     const obj = {key: "", value: 0};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/oneof.js b/test/fixtures/oneof.js
index 9a6c290..8f87ab0 100644
--- a/test/fixtures/oneof.js
+++ b/test/fixtures/oneof.js
@@ -1,5 +1,5 @@
 
-export function readEnvelope(pbf, end = pbf.length) {
+export function readEnvelope(pbf, end) {
     const obj = {id: 0, int: 0, value: undefined, float: 0, string: ""};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/packed.js b/test/fixtures/packed.js
index 6c08a20..1081633 100644
--- a/test/fixtures/packed.js
+++ b/test/fixtures/packed.js
@@ -1,5 +1,5 @@
 
-export function readNotPacked(pbf, end = pbf.length) {
+export function readNotPacked(pbf, end) {
     const obj = {value: [], types: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -14,7 +14,7 @@ export function writeNotPacked(obj, pbf) {
     if (obj.types) for (const item of obj.types) pbf.writeVarintField(2, item);
 }
 
-export function readFalsePacked(pbf, end = pbf.length) {
+export function readFalsePacked(pbf, end) {
     const obj = {value: [], types: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -29,7 +29,7 @@ export function writeFalsePacked(obj, pbf) {
     if (obj.types) for (const item of obj.types) pbf.writeVarintField(2, item);
 }
 
-export function readPacked(pbf, end = pbf.length) {
+export function readPacked(pbf, end) {
     const obj = {value: [], types: []};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/packed_proto3.js b/test/fixtures/packed_proto3.js
index 120f12a..d0fefca 100644
--- a/test/fixtures/packed_proto3.js
+++ b/test/fixtures/packed_proto3.js
@@ -4,7 +4,7 @@ export const MessageType = {
     "GREETING": 1
 };
 
-export function readNotPacked(pbf, end = pbf.length) {
+export function readNotPacked(pbf, end) {
     const obj = {value: [], types: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -19,7 +19,7 @@ export function writeNotPacked(obj, pbf) {
     if (obj.types) pbf.writePackedVarint(2, obj.types);
 }
 
-export function readFalsePacked(pbf, end = pbf.length) {
+export function readFalsePacked(pbf, end) {
     const obj = {value: [], types: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -34,7 +34,7 @@ export function writeFalsePacked(obj, pbf) {
     if (obj.types) for (const item of obj.types) pbf.writeVarintField(2, item);
 }
 
-export function readPacked(pbf, end = pbf.length) {
+export function readPacked(pbf, end) {
     const obj = {value: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -47,7 +47,7 @@ export function writePacked(obj, pbf) {
     if (obj.value) pbf.writePackedVarint(16, obj.value);
 }
 
-export function readPackedFixed(pbf, end = pbf.length) {
+export function readPackedFixed(pbf, end) {
     const obj = {value: []};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/type_string.js b/test/fixtures/type_string.js
index 36f81ac..8d9dbae 100644
--- a/test/fixtures/type_string.js
+++ b/test/fixtures/type_string.js
@@ -1,5 +1,5 @@
 
-export function readTypeString(pbf, end = pbf.length) {
+export function readTypeString(pbf, end) {
     const obj = {int: "0", long: "0", boolVal: false, float: "0", default_implicit: "0", default_explicit: "42"};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -22,7 +22,7 @@ export function writeTypeString(obj, pbf) {
     if (obj.default_explicit != null && obj.default_explicit !== "42") pbf.writeVarintField(6, parseInt(obj.default_explicit, 10));
 }
 
-export function readTypeNotString(pbf, end = pbf.length) {
+export function readTypeNotString(pbf, end) {
     const obj = {int: 0, long: 0, boolVal: false, float: 0};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/varint.js b/test/fixtures/varint.js
index ebc31c1..919cb50 100644
--- a/test/fixtures/varint.js
+++ b/test/fixtures/varint.js
@@ -1,5 +1,5 @@
 
-export function readEnvelope(pbf, end = pbf.length) {
+export function readEnvelope(pbf, end) {
     const obj = {int: 0, uint: 0, long: 0, ulong: 0};
     let field;
     while ((field = pbf.nextField(end))) {
diff --git a/test/fixtures/vector_tile.js b/test/fixtures/vector_tile.js
index 64e8909..086614c 100644
--- a/test/fixtures/vector_tile.js
+++ b/test/fixtures/vector_tile.js
@@ -1,5 +1,5 @@
 
-export function readTile(pbf, end = pbf.length) {
+export function readTile(pbf, end) {
     const obj = {layers: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -19,7 +19,7 @@ export const TileGeomType = {
     "POLYGON": 3
 };
 
-export function readTileValue(pbf, end = pbf.length) {
+export function readTileValue(pbf, end) {
     const obj = {string_value: "", float_value: 0, double_value: 0, int_value: 0, uint_value: 0, sint_value: 0, bool_value: false};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -44,7 +44,7 @@ export function writeTileValue(obj, pbf) {
     if (obj.bool_value) pbf.writeBooleanField(7, obj.bool_value);
 }
 
-export function readTileFeature(pbf, end = pbf.length) {
+export function readTileFeature(pbf, end) {
     const obj = {id: 0, tags: [], type: 0, geometry: []};
     let field;
     while ((field = pbf.nextField(end))) {
@@ -63,7 +63,7 @@ export function writeTileFeature(obj, pbf) {
     if (obj.geometry) pbf.writePackedVarint(4, obj.geometry);
 }
 
-export function readTileLayer(pbf, end = pbf.length) {
+export function readTileLayer(pbf, end) {
     const obj = {version: 1, name: "", features: [], keys: [], values: [], extent: 4096};
     let field;
     while ((field = pbf.nextField(end))) {

From bf66d3674495ecc34a76f7f2d84619ac6e44c073 Mon Sep 17 00:00:00 2001
From: Vladimir Agafonkin <agafonkin@gmail.com>
Date: Tue, 26 May 2026 22:52:51 +0300
Subject: [PATCH 4/5] skip fields implicitly in nextField, drop skipField

---
 README.md                          | 12 +++++-------
 compile.js                         |  1 -
 index.js                           | 10 +++-------
 test/fixtures/defaults.js          |  1 -
 test/fixtures/defaults_implicit.js |  1 -
 test/fixtures/defaults_proto3.js   |  1 -
 test/fixtures/embedded_type.js     |  3 ---
 test/fixtures/map.js               |  3 ---
 test/fixtures/map_collision.js     |  4 ----
 test/fixtures/oneof.js             |  1 -
 test/fixtures/packed.js            |  3 ---
 test/fixtures/packed_proto3.js     |  4 ----
 test/fixtures/type_string.js       |  2 --
 test/fixtures/varint.js            |  1 -
 test/fixtures/vector_tile.js       |  4 ----
 test/pbf.test.js                   |  5 ++---
 16 files changed, 10 insertions(+), 46 deletions(-)

diff --git a/README.md b/README.md
index 9e349ac..9b979a0 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,6 @@ function readData(pbf, end) {
         if (field === 1) data.name = pbf.readString();
         else if (field === 2) data.version = pbf.readVarint();
         else if (field === 3) data.layer = readLayer(pbf, pbf.readVarint() + pbf.pos);
-        else pbf.skipField();
     }
     return data;
 }
@@ -81,7 +80,6 @@ function readLayer(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) layer.name = pbf.readString();
         else if (field === 3) layer.size = pbf.readVarint();
-        else pbf.skipField();
     }
     return layer;
 }
@@ -150,14 +148,13 @@ pbf.pos; // current offset for reading or writing
 
 #### Reading
 
-Loop over a message's fields with `nextField`, dispatch on the field number, and call `skipField()` for anything you don't recognize:
+Loop over a message's fields with `nextField` and dispatch on the field number. Unrecognized or unread fields are skipped automatically on the next iteration:
 
 ```js
 let field;
 while ((field = pbf.nextField(end))) {
     if (field === 1) obj.id = pbf.readVarint();
     else if (field === 2) obj.name = pbf.readString();
-    else pbf.skipField();
 }
 ```
 
@@ -182,7 +179,6 @@ let fooPos = -1;
 let field;
 while ((field = pbf.nextField())) {
     if (field === 1) fooPos = pbf.pos;
-    pbf.skipField();
 }
 ...
 pbf.pos = fooPos;
@@ -204,8 +200,10 @@ Scalar reading methods:
 * `readDouble()`
 * `readString()`
 * `readBytes()`
-* `nextField(end)` — returns the next field number, or `0` at end-of-message
-* `skipField()` — skips the current field
+
+Field iteration methods:
+
+* `nextField(end)` — returns the next field number, or `0` at end-of-message; skips the previous field's value if it wasn't consumed
 * `skip(value)` — skips a field given its raw tag varint
 
 Packed reading methods:
diff --git a/compile.js b/compile.js
index cdbc4fd..aaf6cc8 100644
--- a/compile.js
+++ b/compile.js
@@ -41,7 +41,6 @@ function writeMessage(ctx, options) {
             for (let i = 0; i < fields.length; i++) {
                 code += `        ${i ? 'else ' : ''}if (field === ${fields[i].tag}) ${compileFieldRead(ctx, fields[i])}\n`;
             }
-            code += '        else pbf.skipField();\n';
             code += '    }\n    return obj;\n';
         }
         code += '}\n';
diff --git a/index.js b/index.js
index 723f73d..a6b1a55 100644
--- a/index.js
+++ b/index.js
@@ -21,6 +21,7 @@ export class PbfReader {
         this.dataView = new DataView(this.buf.buffer);
         this.pos = 0;
         this.type = 0;
+        this._valueStart = -1;
         this.length = this.buf.length;
     }
 
@@ -33,9 +34,7 @@ export class PbfReader {
     readFields(readField, result, end = this.length) {
         let field;
         while ((field = this.nextField(end))) {
-            const startPos = this.pos;
             readField(field, result, this);
-            if (this.pos === startPos) this.skipField();
         }
         return result;
     }
@@ -201,17 +200,14 @@ export class PbfReader {
      * @param {number} [end]
      */
     nextField(end = this.length) {
+        if (this.pos === this._valueStart) this.skip(this.type);
         if (this.pos >= end) return 0;
         const tag = this.readVarint();
         this.type = tag & 0x7;
+        this._valueStart = this.pos;
         return tag >>> 3;
     }
 
-    /** Skip the field most recently returned by `nextField`. */
-    skipField() {
-        this.skip(this.type);
-    }
-
     /** @param {number} val */
     skip(val) {
         const type = val & 0x7;
diff --git a/test/fixtures/defaults.js b/test/fixtures/defaults.js
index 61aa3f9..41505c9 100644
--- a/test/fixtures/defaults.js
+++ b/test/fixtures/defaults.js
@@ -13,7 +13,6 @@ export function readEnvelope(pbf, end) {
         else if (field === 3) obj.flag = pbf.readBoolean();
         else if (field === 4) obj.weight = pbf.readFloat();
         else if (field === 5) obj.id = pbf.readVarint(true);
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/defaults_implicit.js b/test/fixtures/defaults_implicit.js
index 90e325f..b7d8a0c 100644
--- a/test/fixtures/defaults_implicit.js
+++ b/test/fixtures/defaults_implicit.js
@@ -24,7 +24,6 @@ export function readEnvelope(pbf, end) {
         else if (field === 8) obj.bytes = pbf.readBytes();
         else if (field === 9) obj.custom = readCustomType(pbf, pbf.readVarint() + pbf.pos);
         else if (field === 10) pbf.readPackedVarint(obj.types);
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/defaults_proto3.js b/test/fixtures/defaults_proto3.js
index 9e405f4..2f0589f 100644
--- a/test/fixtures/defaults_proto3.js
+++ b/test/fixtures/defaults_proto3.js
@@ -13,7 +13,6 @@ export function readEnvelope(pbf, end) {
         else if (field === 3) obj.flag = pbf.readBoolean();
         else if (field === 4) obj.weight = pbf.readFloat();
         else if (field === 5) obj.id = pbf.readVarint(true);
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/embedded_type.js b/test/fixtures/embedded_type.js
index bbff113..ee9244a 100644
--- a/test/fixtures/embedded_type.js
+++ b/test/fixtures/embedded_type.js
@@ -6,7 +6,6 @@ export function readEmbeddedType(pbf, end) {
         if (field === 1) obj.value = pbf.readString();
         else if (field === 4) obj.sub_field = readEmbeddedTypeContainer(pbf, pbf.readVarint() + pbf.pos);
         else if (field === 5) obj.sub_sub_field = readEmbeddedTypeContainerInner(pbf, pbf.readVarint() + pbf.pos);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -21,7 +20,6 @@ export function readEmbeddedTypeContainer(pbf, end) {
     let field;
     while ((field = pbf.nextField(end))) {
         if (field === 1) obj.values.push(readEmbeddedTypeContainerInner(pbf, pbf.readVarint() + pbf.pos));
-        else pbf.skipField();
     }
     return obj;
 }
@@ -34,7 +32,6 @@ export function readEmbeddedTypeContainerInner(pbf, end) {
     let field;
     while ((field = pbf.nextField(end))) {
         if (field === 1) obj.value = pbf.readString();
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/map.js b/test/fixtures/map.js
index 9db7fe9..6966a31 100644
--- a/test/fixtures/map.js
+++ b/test/fixtures/map.js
@@ -5,7 +5,6 @@ export function readEnvelope(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) { const {key, value} = readEnvelopeKvEntry(pbf, pbf.readVarint() + pbf.pos); obj.kv[key] = value; }
         else if (field === 2) { const {key, value} = readEnvelopeKnEntry(pbf, pbf.readVarint() + pbf.pos); obj.kn[key] = value; }
-        else pbf.skipField();
     }
     return obj;
 }
@@ -20,7 +19,6 @@ export function readEnvelopeKvEntry(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readString();
-        else pbf.skipField();
     }
     return obj;
 }
@@ -35,7 +33,6 @@ export function readEnvelopeKnEntry(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readVarint(true);
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/map_collision.js b/test/fixtures/map_collision.js
index 957638f..60c507e 100644
--- a/test/fixtures/map_collision.js
+++ b/test/fixtures/map_collision.js
@@ -7,7 +7,6 @@ export function readEnvelope(pbf, end) {
         else if (field === 2) { const {key, value} = readEnvelopeKnEntry$(pbf, pbf.readVarint() + pbf.pos); obj.kn[key] = value; }
         else if (field === 3) obj.sibling = readEnvelopeKvEntry(pbf, pbf.readVarint() + pbf.pos);
         else if (field === 4) obj.flag = pbf.readVarint();
-        else pbf.skipField();
     }
     return obj;
 }
@@ -28,7 +27,6 @@ export function readEnvelopeKvEntry(pbf, end) {
     let field;
     while ((field = pbf.nextField(end))) {
         if (field === 1) obj.marker = pbf.readVarint(true);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -42,7 +40,6 @@ export function readEnvelopeKvEntry$(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readString();
-        else pbf.skipField();
     }
     return obj;
 }
@@ -57,7 +54,6 @@ export function readEnvelopeKnEntry$(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) obj.key = pbf.readString();
         else if (field === 2) obj.value = pbf.readVarint(true);
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/oneof.js b/test/fixtures/oneof.js
index 8f87ab0..5ac7bb1 100644
--- a/test/fixtures/oneof.js
+++ b/test/fixtures/oneof.js
@@ -7,7 +7,6 @@ export function readEnvelope(pbf, end) {
         else if (field === 2) { obj.int = pbf.readVarint(true); obj.value = "int"; }
         else if (field === 3) { obj.float = pbf.readFloat(); obj.value = "float"; }
         else if (field === 4) { obj.string = pbf.readString(); obj.value = "string"; }
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/packed.js b/test/fixtures/packed.js
index 1081633..1e6a7f0 100644
--- a/test/fixtures/packed.js
+++ b/test/fixtures/packed.js
@@ -5,7 +5,6 @@ export function readNotPacked(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types, true);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -20,7 +19,6 @@ export function readFalsePacked(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types, true);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -35,7 +33,6 @@ export function readPacked(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types, true);
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/packed_proto3.js b/test/fixtures/packed_proto3.js
index d0fefca..9935d32 100644
--- a/test/fixtures/packed_proto3.js
+++ b/test/fixtures/packed_proto3.js
@@ -10,7 +10,6 @@ export function readNotPacked(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -25,7 +24,6 @@ export function readFalsePacked(pbf, end) {
     while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedVarint(obj.value, true);
         else if (field === 2) pbf.readPackedVarint(obj.types);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -39,7 +37,6 @@ export function readPacked(pbf, end) {
     let field;
     while ((field = pbf.nextField(end))) {
         if (field === 16) pbf.readPackedVarint(obj.value, true);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -52,7 +49,6 @@ export function readPackedFixed(pbf, end) {
     let field;
     while ((field = pbf.nextField(end))) {
         if (field === 1) pbf.readPackedSFixed64(obj.value);
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/type_string.js b/test/fixtures/type_string.js
index 8d9dbae..236adac 100644
--- a/test/fixtures/type_string.js
+++ b/test/fixtures/type_string.js
@@ -9,7 +9,6 @@ export function readTypeString(pbf, end) {
         else if (field === 4) obj.float = pbf.readFloat().toString();
         else if (field === 5) obj.default_implicit = pbf.readVarint(true).toString();
         else if (field === 6) obj.default_explicit = pbf.readVarint(true).toString();
-        else pbf.skipField();
     }
     return obj;
 }
@@ -30,7 +29,6 @@ export function readTypeNotString(pbf, end) {
         else if (field === 2) obj.long = pbf.readVarint(true);
         else if (field === 3) obj.boolVal = pbf.readBoolean();
         else if (field === 4) obj.float = pbf.readFloat();
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/varint.js b/test/fixtures/varint.js
index 919cb50..9592b6c 100644
--- a/test/fixtures/varint.js
+++ b/test/fixtures/varint.js
@@ -7,7 +7,6 @@ export function readEnvelope(pbf, end) {
         else if (field === 2) obj.uint = pbf.readVarint();
         else if (field === 3) obj.long = pbf.readVarint(true);
         else if (field === 4) obj.ulong = pbf.readVarint();
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/fixtures/vector_tile.js b/test/fixtures/vector_tile.js
index 086614c..fd91b4a 100644
--- a/test/fixtures/vector_tile.js
+++ b/test/fixtures/vector_tile.js
@@ -4,7 +4,6 @@ export function readTile(pbf, end) {
     let field;
     while ((field = pbf.nextField(end))) {
         if (field === 3) obj.layers.push(readTileLayer(pbf, pbf.readVarint() + pbf.pos));
-        else pbf.skipField();
     }
     return obj;
 }
@@ -30,7 +29,6 @@ export function readTileValue(pbf, end) {
         else if (field === 5) obj.uint_value = pbf.readVarint();
         else if (field === 6) obj.sint_value = pbf.readSVarint();
         else if (field === 7) obj.bool_value = pbf.readBoolean();
-        else pbf.skipField();
     }
     return obj;
 }
@@ -52,7 +50,6 @@ export function readTileFeature(pbf, end) {
         else if (field === 2) pbf.readPackedVarint(obj.tags);
         else if (field === 3) obj.type = pbf.readVarint();
         else if (field === 4) pbf.readPackedVarint(obj.geometry);
-        else pbf.skipField();
     }
     return obj;
 }
@@ -73,7 +70,6 @@ export function readTileLayer(pbf, end) {
         else if (field === 3) obj.keys.push(pbf.readString());
         else if (field === 4) obj.values.push(readTileValue(pbf, pbf.readVarint() + pbf.pos));
         else if (field === 5) obj.extent = pbf.readVarint();
-        else pbf.skipField();
     }
     return obj;
 }
diff --git a/test/pbf.test.js b/test/pbf.test.js
index 77e7950..0ff128c 100644
--- a/test/pbf.test.js
+++ b/test/pbf.test.js
@@ -445,7 +445,7 @@ test('write a raw message > 0x10000000', () => {
     assert.deepEqual(bytes.subarray(encodedSize.length, encodedSize.length + markerSize), encodedMarker);
 });
 
-test('nextField & skipField', () => {
+test('nextField implicitly skips unread fields', () => {
     // Encode three fields: varint #1 = 42, string #2 = "hi", varint #3 = 7.
     const w = new PbfWriter();
     w.writeVarintField(1, 42);
@@ -453,14 +453,13 @@ test('nextField & skipField', () => {
     w.writeVarintField(3, 7);
     const buf = w.finish();
 
-    // Reader that only knows field 1 and field 3 — field 2 must be skipped via skipField.
+    // Reader that only knows field 1 and field 3 — field 2 is skipped implicitly.
     const pbf = new PbfReader(buf);
     const seen = {};
     let field;
     while ((field = pbf.nextField())) {
         if (field === 1) seen.a = pbf.readVarint();
         else if (field === 3) seen.b = pbf.readVarint();
-        else pbf.skipField();
     }
     assert.deepEqual(seen, {a: 42, b: 7});
     assert.equal(pbf.pos, buf.length);

From f85f99053933b9b55141201e98f9e0aa661aa6d6 Mon Sep 17 00:00:00 2001
From: Vladimir Agafonkin <agafonkin@gmail.com>
Date: Thu, 28 May 2026 14:49:49 +0300
Subject: [PATCH 5/5] 5.1.0

---
 package-lock.json | 4 ++--
 package.json      | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index a7e9101..10f2500 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "pbf",
-  "version": "5.0.0",
+  "version": "5.1.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "pbf",
-      "version": "5.0.0",
+      "version": "5.1.0",
       "license": "BSD-3-Clause",
       "dependencies": {
         "resolve-protobuf-schema": "^2.1.0"
diff --git a/package.json b/package.json
index bb9e97c..4a3b997 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "pbf",
-  "version": "5.0.0",
+  "version": "5.1.0",
   "description": "a low-level, lightweight protocol buffers implementation in JavaScript",
   "main": "index.js",
   "type": "module",